This invention relates to urethane foam which is orthogonally reinforced with filaments to provide an effective cryogenic thermal insulation, and is particularly concerned with the provision of novel apparatus and a novel method for inserting fiber, particularly glass, filaments as the Z or third axis vertical filaments of an orthogonal reinforcement including X or longitudinal filaments and Y or transverse filaments, for use as reinforcement in producing urethane foam cryogenic insulation.
In our copending application Ser. No. 516,412 filed Oct. 21, 1974, now abandoned, and in our copending application Ser. No. 669,819, filed Mar. 24, 1976, which is a continuation-in-part of Ser. No. 516,412, there is disclosed a method of continuously forming three-dimensional filament reinforced foam insulation by extending Z or vertically disposed fibers through vertically spaced layers of spaced X fibers in the longitudinal direction and spaced Y fibers in a transverse direction. Although this method has been found effective, it necessitates the formation of an arrangement employing four strands of Z fibers for each opening between the X and Y fibers, and wherein lengths of such initially parallel strands are brought together at spaced intervals to form a chain of alternate grouped and spaced fibers forming segments. This is a relatively complex procedure and operation.
It is of importance to insert vertical or Z fibers in layers of X and Y fibers in providing fiber reinforcement for urethane foam insulation in order to achieve load bearing qualities for the final cryogenic insulation foam products. The fibers carry tensile and compressive loads to transmit and distribute plank to plank forces through the adhesive system which cements the urethane foam insulation planks into a continuous multi-layered structure to provide an operational cryogenic thermal insulation system. For this purpose, the Z fibers, e.g. fiberglass yarn, are inserted into the multi-layered X-Y grid, the Z yarns preferably being stiffened as by a coating of cured resin. The X-Y-Z array of reinforcement fibers is then filled with foam, such as polyurethane rigid closed cell foam, so that all of the array yarns are fully captured, the resulting urethane foam planks then being fully load bearing.
One use of such reinforced cryogenic foam insulation is in insulating compartments or holds of marine vessels used to transport liquid natural gas (LNG). Another important application is in insulating static cryogenic liquid tanks or containers.
It is accordingly an object of the present invention to provide novel apparatus and a novel method for inserting third axis or Z fibers into an orthogonal reinforcement formed of layered X-Y fibers, to provide reinforcement for cryogenic foam insulation. A particular object is the provision of novel and simple apparatus and a simple method for efficiently inserting a single strand, or a group of strands, e.g. of glass fiber, preferably impregnated with a stiffening resin, into vertically aligned openings between X and Y oriented fibers in vertically stacked X-Y layers, to form an X-Y-Z reinforcement array which can be filled with foam insulation to provide a cryogenic thermal insulation.